In what context or under what circumstances is the deinit method called in Swift?

The deinit method in Swift is called automatically just before an instance of a class is deallocated from memory. It is a destructor that allows you to release resources, close files, cancel observers, and perform other cleanup.

deinit is called in the following circumstances:

• When the reference count to the object reaches zero (ARC — Automatic Reference Counting).
• Before the object is deinitialized and memory is freed.

Example of using deinit:

class FileHandler {
    let fileName: String

    init(fileName: String) {
        self.fileName = fileName
        print("File opened: \(fileName)")
    }

    deinit {
        print("File closed: \(fileName)")
    }
}

func example() {
    let handler = FileHandler(fileName: "data.txt")
    // handler is used inside the function
} // here, handler goes out of scope, deinit is called

Thus, deinit is useful for managing resources and cleanup when an object is destroyed.